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We conducted an institutional review board-approved study to examine the relationship between the body mass index (BMI) of women diagnosed with a urinary tract infection (UTI) and the rate of urine sample contamination. Based on our clinical experience, we hypothesized that obese women are more likely to provide contaminated clean-catch urine samples than non-obese women. Our results lent support to that hypothesis.
We retrospectively analyzed a 6-month convenience sample of urine culture (UC) results from patients in a large health care system. Inclusion criteria were: female sex, BMI information available, clean-catch urine sample, UC obtained, and diagnosis of UTI. Patients were excluded if they were pregnant. Two researchers independently evaluated each UC to determine if the UC was consistent with the diagnosis of UTI and if it showed evidence of contamination (based on previously accepted standards and definitions).
Out of 7134 UCs analyzed, 50.1% showed some variable of contamination, 26.4% were consistent with the diagnosis of UTI, and 30.4% of the positive UCs had contamination.
Rates of positive UC were stable regardless of BMI. This refutes prior studies that suggested an increased BMI is associated with an increased risk of UTI. And, compared to patients with a BMI <35 kg/m2, having a BMI >35 kg/m2 was associated with more frequent contamination (odds ratio=1.41) and higher rates of abnormal markers used for diagnosing UTIs, including nitrites, white blood cells, and bacteria.
Physicians should consider these results when assessing for, or diagnosing, UTI to avoid misdiagnosis and overtreatment. We suggest that physicians have an assistant help very obese patients with the urine specimen collection process, consider catheterization if an accurate diagnosis is critical, or await UC results before initiating treatment.
Michael Zwank, MD
Ryan Bourdon, MD
Saint Paul, Minn
We conducted an institutional review board-approved study to examine the relationship between the body mass index (BMI) of women diagnosed with a urinary tract infection (UTI) and the rate of urine sample contamination. Based on our clinical experience, we hypothesized that obese women are more likely to provide contaminated clean-catch urine samples than non-obese women. Our results lent support to that hypothesis.
We retrospectively analyzed a 6-month convenience sample of urine culture (UC) results from patients in a large health care system. Inclusion criteria were: female sex, BMI information available, clean-catch urine sample, UC obtained, and diagnosis of UTI. Patients were excluded if they were pregnant. Two researchers independently evaluated each UC to determine if the UC was consistent with the diagnosis of UTI and if it showed evidence of contamination (based on previously accepted standards and definitions).
Out of 7134 UCs analyzed, 50.1% showed some variable of contamination, 26.4% were consistent with the diagnosis of UTI, and 30.4% of the positive UCs had contamination.
Rates of positive UC were stable regardless of BMI. This refutes prior studies that suggested an increased BMI is associated with an increased risk of UTI. And, compared to patients with a BMI <35 kg/m2, having a BMI >35 kg/m2 was associated with more frequent contamination (odds ratio=1.41) and higher rates of abnormal markers used for diagnosing UTIs, including nitrites, white blood cells, and bacteria.
Physicians should consider these results when assessing for, or diagnosing, UTI to avoid misdiagnosis and overtreatment. We suggest that physicians have an assistant help very obese patients with the urine specimen collection process, consider catheterization if an accurate diagnosis is critical, or await UC results before initiating treatment.
Michael Zwank, MD
Ryan Bourdon, MD
Saint Paul, Minn
We conducted an institutional review board-approved study to examine the relationship between the body mass index (BMI) of women diagnosed with a urinary tract infection (UTI) and the rate of urine sample contamination. Based on our clinical experience, we hypothesized that obese women are more likely to provide contaminated clean-catch urine samples than non-obese women. Our results lent support to that hypothesis.
We retrospectively analyzed a 6-month convenience sample of urine culture (UC) results from patients in a large health care system. Inclusion criteria were: female sex, BMI information available, clean-catch urine sample, UC obtained, and diagnosis of UTI. Patients were excluded if they were pregnant. Two researchers independently evaluated each UC to determine if the UC was consistent with the diagnosis of UTI and if it showed evidence of contamination (based on previously accepted standards and definitions).
Out of 7134 UCs analyzed, 50.1% showed some variable of contamination, 26.4% were consistent with the diagnosis of UTI, and 30.4% of the positive UCs had contamination.
Rates of positive UC were stable regardless of BMI. This refutes prior studies that suggested an increased BMI is associated with an increased risk of UTI. And, compared to patients with a BMI <35 kg/m2, having a BMI >35 kg/m2 was associated with more frequent contamination (odds ratio=1.41) and higher rates of abnormal markers used for diagnosing UTIs, including nitrites, white blood cells, and bacteria.
Physicians should consider these results when assessing for, or diagnosing, UTI to avoid misdiagnosis and overtreatment. We suggest that physicians have an assistant help very obese patients with the urine specimen collection process, consider catheterization if an accurate diagnosis is critical, or await UC results before initiating treatment.
Michael Zwank, MD
Ryan Bourdon, MD
Saint Paul, Minn